The present invention is directed towards an efficient battery charger, and more specifically, to an efficient multiple battery charger having an improved power controller that senses the power demand on each battery and provides the minimum output voltage required to charge all, including the battery with greatest demand.
In battery powered portable electronic systems the portable power supply is usually provided by either disposable batteries, replaceable batteries, such as Nickel Cadmium (NiCd), or other rechargeable batteries. The disposable batteries are well known, but are not rechargeable. Since many users desire to use their electronic device without regard to whether an electrical outlet is available to power the device, such consumers typically rely on rechargeable batteries to power the device. One such type of battery is the rechargeable battery, which typically requires a dedicated battery charger. Another type of battery is a battery pack specifically designed for the portable electronic device. In this type of device, the manufacturer of the device allows the battery pack to be replaceable so that a second battery source can be carried to replace the first pack in the event that the first battery pack has its charge depleted. The next type of batteries are those intended to be permanently installed in the device. Once the batteries are drained of their energy, either they must be recharged or the device must be powered by an alternative power source before the device can resume operation.
In devices that use either separate battery power packs or internal batteries, several batteries are charged during the same recharging session. Most frequently, each battery is at a different voltage level from the others in the pack. This leads to an inefficient charging scheme when all batteries are being recharged simultaneously. Alternatively, some systems attempt to recharge each battery separately from the others, but do so in a manner that is highly inefficient in that the charging load does not adjust as the voltage charge on each battery reaches a full charge state. This power loss is usually in the form of heat, which can be damaging to the electronic device if any of the fail safe mechanisms in the device fail under certain circumstances.
Accordingly, what is needed is a battery charger with a power controller that operates at the minimum voltage possible in order to reduce power loss and heat. Furthermore, the power charger should be able to respond to peak loads when used in combination with the powering of the electronic device while charging the batteries to operate the device without interfering with system performance.